A huge market exists for disk drives for mass-market computing devices such as desktop computers and laptop computers, as well as small form factor (SFF) disk drives for use in mobile computing devices (e.g. personal digital assistants (PDAs), cell-phones, digital cameras, etc.). To be competitive, a disk drive should be relatively inexpensive and provide substantial capacity, rapid access to data, and reliable performance.
Disk drives typically employ a moveable head actuator to frequently access large amounts of data stored on a disk. One example of a disk drive is a hard disk drive. A conventional hard disk drive has a head disk assembly (“HDA”) including at least one magnetic disk (“disk”), a spindle motor for rapidly rotating the disk, and a head stack assembly (“HSA”) that includes a head gimbal assembly (HGA) with a moveable transducer head for reading and writing data. The HSA forms part of a servo control system that positions the moveable transducer head over a particular track on the disk to read or write information from and to that track, respectively.
Typically, a conventional hard disk drive includes a disk having a plurality of concentric tracks. Each surface of each disk conventionally contains a plurality of concentric data tracks angularly divided into a plurality of data sectors. In addition, special servo information may be provided on each disk to determine the position of the moveable transducer head.
The most popular form of servo is called “embedded servo” wherein the servo information is written in a plurality of servo sectors that are angularly spaced from one another and are interspersed between data sectors around each track of each disk.
A significant problem that can occur in hard disk drives relates to data loss that may be caused by interruptions in the power signal supplied by the host computer. For example, a power loss may occur that causes a write data sector operation to terminate prematurely resulting in commanded write data to not actually be written to the data sector of the disk.
Hard disk controllers typically have an abort mechanism that causes currently active write operations to the disk to halt upon the detection of a reset signal due to a loss of power from the host computer. In the abort mechanism, the write-gate signal is removed immediately and additional data that was commanded to be written to the data sector is not written causing a “write-splice” on the disk at the point where the write-gate was removed. The write-splice causes any subsequent read operations of the data sector with the write-splice to return an uncorrectable error correction code (ECC) error back to the host computer.
Thus, data may be permanently lost and ECC errors may occur. Further, this may result in the destruction of some types of software applications. In some instances, where a write-splice occurs in portions of the disk that relate to the operating system, the host computer may become unbootable and unusable.
There is therefore a need for a disk drive that addresses these limitations by eliminating the possibility of a write-splice occurring on the disk due to a power loss.